// -*- mode: c++; mode: auto-fill; -*-

#include <stdio.h>

typedef unsigned int dword;

struct PAKENTRY
{
  char szFileName[32]; // XORed by 0xff
  dword dwSize;
  dword dwOffset;
};

struct PAKHEADER
{
  dword dwSignature;
  dword dwFilesAmount;
};

void unmaskFileName(char* p)
{
  char* pw = p;
  while(*p)
  {
    *p++ ^= 0xff;
  }
}

int usage()
{
  printf("extbgm -- TH2X BGM/SE extractor\n"
         "Usage: extbgm {bgm.pak|se.pak}\n");
  return 1;
}

int main(int ac, char** av)
{
  if(!*++av)
    return usage();

  FILE* fi = fopen(*av, "rb");
  if(!fi)
    return usage();

  PAKHEADER header;

  fread(&header, sizeof header, 1, fi);

  if(header.dwSignature != '\0CAL')
    return usage();
  
  for(int i = 0; i < header.dwFilesAmount; i++)
  {
    PAKENTRY entry;
    fread(&entry, sizeof entry, 1, fi);
    int entrypos = ftell(fi);
    unmaskFileName(entry.szFileName);
    printf("%-32s  offset: 0x%08x  size: 0x%08x\n",
           entry.szFileName, entry.dwOffset, entry.dwSize);
    fseek(fi, entry.dwOffset, SEEK_SET);
    FILE* fo = fopen(entry.szFileName, "wb");
    unsigned char buffer[1 << 16];
    int nBytesToCopy = entry.dwSize, nBytesRead, nBytesToWrite;
    while(nBytesToCopy > 0)
    {
      nBytesRead = fread(buffer, 1, 1 << 16, fi);
      
      if(nBytesToCopy < nBytesRead)
      { 
        nBytesToWrite = nBytesToCopy;
        nBytesToCopy = 0;
      }
      else
      {
        nBytesToWrite = nBytesRead;
        nBytesToCopy -= nBytesRead;
      }
      fwrite(buffer, 1, nBytesToWrite, fo);
      putchar('o');
    }
    putchar('\n');
    fclose(fo);
    fseek(fi, entrypos, SEEK_SET);
  }

  fclose(fi);

}